Controlling vegetation with alkenyl thiopyridine oxides



United States Patent 3 107 994 CONTROLLING VEGETATION WITH ALKENYL THIOPYRIDINE OXIDES Herbert L. Rawlings, Scott Depot, and John I. DAmico,

Charleston, W. Va., assignors to Monsanto Chemical Company, St. Louis, Mo., a corporation of Delaware No Drawing. Original application May 1, 1959, Ser. No. 810,225. Divided and this application June 3, 1960, Ser. No. 47,573

12 Claims. (Cl. 712.5)

in which R represents a lower alkenyl group, preferably halogen substituted lower alkenyl. They are prepared by condensing the sodium salt of 2-pyridinethiol, l-oxide with the corresponding unsaturated halide. Suitable reactants comprise allyl chloride, methallyl chloride, cisl,2,3-trichloro-2-butene, trans-1,2,3-trichloro 2 butene, 1,3-dichloro-2-butene, 2,3-dichloro-l-propane, 2,3-dibromo-l-propene, 1,3-dichloropropene, 1-chloro-3-iodo- Z-propene, 1,3-diiodo-2-butene, 2,3-diiodo-2-butene, 3- bromo-l-chloro-Z-fluoro-l-propene, cis-1,2,3-trichloro-1- propene, trans-1,2,3-trichloro-l-propene, l,4-dibromo-2,3- diehloro-2-butene, 1,2,3,3-tetrachloropropene and 2,3,3 trichloro-l-butene. The last readily undergoes an allylic rearrangement and is therefore equivalent to 1,2,3-trichIoro-Z-butene.

The following examples illustrate in detail the preparation and properties of some of the new products but are not intended as a limitation of the invention.

EXAMPLE 1 To a stirred solution of 30 grams (0.2 mole) of the sodium salt of Z-thiopyridine, l-oxide in 100 ml. of water was added in one portion 22.2 grams (0.2 mole) of 2,3-dichloro-l-propene and the mixture heated at 50-60" C. for 24 hours. After cooling to 10 C., 300 ml. of ether were added and stirring continued for 15 minutes at --10 C. The precipitate which formed was filtered and air dried at room temperature. After recrystallization from ethyl alcohol, the 2-(2-chloroallylthio)-pyridine, l-oxide was obtained as a tan solid, M.P. ll4l15 C. Analysis gave 7.4% nitrogen, 15.6% sulfur and 17.6% chlorine as compared to 7.0% nitrogen, 15.9% sulfur and 17.6% chlorine calculated for C H CINOS.

EXAMPLE 2 In this example 2-bromo-3-chloro-1-propene was used in place of 2,3-dichloro-l-propene. The mixture was heated at 50-60" C. for 5 hours, then cooled to C. and 500 ml. of ether added. Stirring was continued at 0-l0 C. for 30 minutes. The precipitate which formed was filtered, washed with water until neutral to litmus and air dried at room temperature. After recrystallization from ethyl alcohol the 2-(2-bromoallylthio)pyridine, l-oxide was obtained as a tan solid, M.P. 122123 C. Analysis gave 5.3% nitrogen and 13.3% sulfur as compared to 5.7% nitrogen and 13.0% sulfur calculated for C H BrN0S.

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EXAMPLE 3 To 30 grams (0.2 mole) of the sodium salt of 2-thiopyridine, l-oxide in 100 ml. of water was added in one portion with stirring 22.2 grams (0.2 mole) of 1,3-dichloropropene and the mixture heated at 50-60 C. for 24 hours. After cooling to 25 C., 300 ml. of ether was added and the solution stirred for one hour. The ether and aqueous layer were then decanted and the bottom oily layer placed in vacuo at a maximum temperature of -90 C. at l-2 mm. The 2-(3-chloroallylthio)pyridine, l-oxide thus obtained was an amber oil'analyzing 6.5% nitrogen and 15.2% sulfur as compared to 6.9% nitrogen and 15.9% sulfur calculated for C H ClNOS.

EXAMPLE 4 In the procedure of Example 3, 1,1,3-trichloropropene was substituted for the 1,3dichloropropene. The 2-(3,3- dichloroallylthio)pyridine, l-oxide was a dark amber oil analyzing 13.4% sulfur as compared to 13.6% calculated fOl' CgHqClgNOS.

EXAMPLE 5 Substitution of cisand trans-1,2,3-trichloropropene in this example gave 2-(cisand trans-2,3-dichloroallylthio)- pyridine, l-oxide as a dark amber oil which became a semi-solid on standing. Analysis gave 5.8% nitrogen and 13.7% sulfur as compared to 5.9% nitrogen and 13.6% sulfur calculated for CgHqClgNOS- EXAMPLE 6 To a stirred solution of 30 grams (0.2 mole) of the sodium salt of Z-thiopyridine, l-oxide in 250 ml. of ethyl alcohol was added 15.3 grams (0.2 mole) of allyl chlo ride and the mixture heated at about 50 C. for 3 hours. The temperature was then raised to 80 C. and heating continued for 2 hours. After cooling, by-product salt was removed by filtration and most of the solvent was then stripped off by distillation at atmospheric pressure. The residue was filtered through Attapulgus clay, the residual solvent removed under vacuum at 7090 C. to yield a dark brown liquid which solidified on standing. The crude product was dissolved in benzene and washed with 52 ml. of 5% caustic soda. Three layers separated on standing. The bottom and top layers were combined and stripped of solvent to C. bath temperature at about 1 mm. Hg. The 2-(allylthio)pyridine, l-oxide was obtained in the form of brown crystals, M.P. 57-63 C. Analysis gave 19.3% sulfur as compared to 19.2% calculated for C H NOS.

The new compounds of this invention have general herbicidal properties but are particularly effective as preemergent herbicides in a wide range of crops and weed species. The method of controlling vegetation, according to this invention, comprises applying thereto a toxic concentration of the above-defined alkenyl thiopyridine oxides. By applying the toxicants to vegetation is meant any means whereby the toxicant is brought into contact with living plants. The toxicant may be applied conveniently in the form of a spray containing the active ingredient in a concentration within the range of 0.1%- l0.0% by weight. Thorough coverage of the foliage is effective for contact killing. For pre-emergenoe control amounts within the range of /260 pounds per acre have been used successfully. I

In general, in the application of these compounds, aqueous dispersions or aqueous solutions depending on whether or not the compound is water soluble, will be found most desirable. The dispersions will of course contain a dispersing or wetting agent and the solutions also I preferably contain wetting agents to facilitate the spreading of the solution. there may be employed soft or hard sodium or potassium As dispersing and wetting agents soaps, alkylated aromatic sodium sulfonates such as sodium dodecylbenzenesulfonate, or an amine salt of dodecylbenzenesulfonic acid, alkali metal salts of sulfated fatty alcohols, ethylene oxide condensation products of Employed at lower concentrations the herbicidal compositions of this invention may be applied to crop plants to give substantially complete control of certain weeds without harming the crop plants. In applying the heralkyl phenols or tall oil and other dispersing and wetting bicidal compositions for selective weed control, the apagents, plications are preferably of the pre-emergence type. At

The tables below illustrate characteristic herbicidal a concentration of 5 pounds per acre, for example, the activity of the compounds of this invention The toxicant compositions show a highly selective action against crab was emulsified in water and the emulsion applied as a grass andpigweed in the presence of such common crops spray. In the pre-emergence teststhe spray was applied as radish, corn and cotton. I to the ground of seeded plots before the grass or other T ese c mpou are also 6166116!!! fllhglcldesy plants emerged. The alkenyl thiopyridine oxide was apcontrol 6611381 11153 against which 'ihcy hmflioh 88 plied at the rate of 25 pounds per acre and the phyeradicams- In View of the low toxicity to grams l p totoxicity observed. In the foliage tests the spray concation to the fhliage is fcasihley w taining the concentration of the active ingredient shown comehlrafiohs are neededcompounds descfihCd i h t bl was li d t th f li f grass d t fl herein eradicated wheat rust (Puccinia rubigo-vera tritici) foliage of bean plants and finally to the foliage of a mixat concentrations Within {hi0 range of 500-2500 P3113 P ture of broadleaved plants and the elfect recorded. The ml'lhOIl- Aqueous dispersions of toxicams Within thc following phytotoxicity rating key was used: aforesaid concentration were applied to wheat plants four days after infection with the fungus. After a week the Contact Preplants were examined and graded as to number and size of pustules formed on the leaves. Fair to excellent control was observed. gg gi g ggfigg 2 It is intended to cover all changes and modifications of Moderate phytotoxicity--- 2 2 the examples of the invention herein chosen for purposes gggg g of disclosure which do not constitute departures from the a spirit and scope of the invention.

The plants employed in the pre-emergence tests are What is claimed is: designated by letter in Table I. The plants corresponding 1. The method of controlling vegetation which comt0 the letters a e a s: prises applying thereto a phytotoxic concentration of a 2- A Moming glory (alkenylthio)pyridine, l-oxide having the general formula B-Wild oats CBrome grass DRye grass E--Radish-mustard l FSugar-b f. 5.4; GCo.. \N HCorn A JFoxtail 40 K-Barnyard grass LCrab grass where R is selected from the class consisting of lower M-Pigweed alkenyl and halogen substituted lower alkenyl. N-Wild buckwheat V 2. The method of controlling vegetation which com- OTomato t prises applying thereto a phytotoxic concentration of 2- P-Sorghum (2-chloroallylthio)pyridine, l-oxide.

Table I PRE-EMERGENCE Phytotoxlclty Rating Compound A B c 1) E F G H J K L M N o P Product of Example 1 0 3 3 3 0 2 0 3 3 2 3 3 Product of Exsmple2 0 3 2 3 0 1 1 3 3 1 3 l Product of Example 3... 0 1 2 3 0 2 2 3 3 0 2 2 Product of Example4 3 '3 3 l 3 3 3 3 1 0 3 ProductoiExample 5 2 3 3 1 3 3 3 3 3 2 3 Product of Example 6. 0 l 2 2 3 3 3 3 3 Table II 3. The method of controlling vegetation which com- CONTACT prises applying thereto a phytotosic concentration of 2- (2-bromoallylthio)pyridine, l-oxide. Phytotoxiclty Rating 4. The method of controlling vegetation which com- Acuve Ingredient 522" prises applying thereto a phytotoxic concentration of 2-(3- will Grass Bean g chloroallylthio) pyridine, I-oxide.

5. The method of controlling vegetation which com M 1 3 3 prises applying thereto a phytotoxic concentration of 2- Pmducm Example 1 0.2 1 1 2 (3,3,-dichloroallythio)pyridine, l-oxide. \1/ i Exam) 182 8;? i i 3 .6. The method of controlling vegetation which comroduet oi Example 3 Q2 0 2 0 u 5 2 3 3 prises applying thereto a phytotoxtc concentration of 4 3-: g g 2-(2,3-dichloroallythio)pyridine, l-oxide. Pmduc 012 o a 2 7. A herbicidal composition comprising a major pro- Product or Example 6 3:; i g 3 portion of a herbicidal adjuvant as carrier, a wetting agent and a minor proportion, sufiicient to exert phytotoxicity,

of a phytotoxic 2-(alkenylthio)pyridine, l-oxide having the general formula where R is selected from the class consisting of lower alkenyl and halogen substituted lower alkenyl.

8. A herbicidal composition comprising a major proportion of a herbicidal adjuvant as carrier, a wetting agent and a minor proportion, suflicient to exert phytotoxicity, of 2-(2-chloroallylthio)pyridine, l-oxide.

9. A herbicidal composition comprising a major proportion of a herbicidal adjuvant as carrier, a wetting agent and a minor proportion, sufiicient to exert phytotoxicity, of 2-(2-bromoallylthio)pyridine, l-oxide.

10. A herbicidal composition comprising a major proportion of a herbicidal adjuvant as carrier, a wetting agent and a minor proportion, sufiicient to exert phytotoxicity, of 2-(3-chloroallylthio)pyridine, l-oxide.

11. A herbicidal composition comprising a major proportion of a herbicidal adjuvant as carrier, a wetting agent and a minor proportion, sufiicient to exert phytotoxicity, of 2-(3,3-dichloroallylthio)P ridine, l-oxide.

12. A herbicidal composition comprising a major pro portion of a herbicidal adjuvant as carrier, a wetting agent and a minor proportion, sufficient to exert phytotoxicity, of 2-(2,3-dichloroallythio)pyridine, l-oxide.

References Cited in the file of this patent UNITED STATES PATENTS 2,922,793 Rockett Jan. 26, 1960 

1. THE METHOD OF CONTROLLING VEGETATION WHICH COMPRISES APPLYING THERETO A PHYTOTOXIC CONCENTRATION OF A 2(ALKENYLTHIO)PYRIDINE, 1-OXIDE HAVING THE GENERAL FORMULA 